The present disclosure relates to discrete fracture networks and, more particularly, to determining the robustness of discrete fracture network permeability estimates.
Boreholes are drilled into earth formations having reservoirs of hydrocarbons in order to extract the hydrocarbons through the boreholes to the surface. Selecting a location at which to drill a borehole is largely dependent on the permeability of the earth formation or ability to flow fluids through pores and fractures of the earth formation. Numerical computational approaches have been used to simulate fractured reservoirs. Typically, these methods are computational time intensive and may cause certain variables to be ignored for simplicity.
Upscaling techniques are often utilized in order to obtain the equivalent permeability of a DFN. Upscaling techniques include an analytical method proposed by M. Oda (see Oda, M., 1985, “Permeability Tensor for Discontinuous Rock Masses.”, Geotechnique, Vol. 35, pp. 483-495) and a range of numerical methods with different applied boundary conditions. Oda's method is an analytical method and hence it is fast. However, it neglects the connectivity between fractures and is not valid for less connected DFNs. Numerical methods for calculating permeability on the other hand depend on the boundary conditions across the DFN, and require more computation time than Oda's method.